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T O P I C R E V I E W

Robert Pearlman

NASA release

NASA's Stardust spacecraft now has a new assignment. Stardust will use flight-proven hardware to perform a new, previously unplanned, investigation.

The newly selected mission of opportunity is called New Exploration of Tempel 1 (NExT).

The mission will reuse NASA's Stardust spacecraft to revisit comet Tempel 1. This investigation will provide the first look at the changes to a comet nucleus produced after its close approach to the sun. It will mark the first time a comet has ever been revisited. NExT also will extend the mapping of Tempel 1, making it the most mapped comet nucleus to date. This mapping will help address the major questions of comet nucleus "geology" raised by images of areas where it appears material might have flowed like a liquid or powder. The images were returned by Deep Impact from its encounter with the comet on July 4, 2005. NExt is scheduled to fly by Tempel 1 on Feb. 14, 2011.

Stardust launched in Feb. 7, 1999. It traveled over 2 billion miles to fly within 150 miles of the comet Wild 2 in January 2004 to bring back samples that may provide new insights into the composition of comets and how they vary from one another. The container with the comet samples returned to Earth in January 2006 while the rest of the spacecraft remained in space.

Just over two weeks before its flyby of comet Tempel 1, NASA's Stardust spacecraft fired its thrusters to help refine its flight path toward the comet. The Stardust-NExT mission will fly past comet Tempel 1 on Valentine's Day (Feb. 14, 2011).

The trajectory correction maneuver, which adjusts the spacecraft's flight path, began at about 4 p.m. EST (1:00 p.m. PST) on Monday, Jan. 31. The Stardust spacecraft's rockets fired for 130 seconds, consumed about 300 grams (10.6 ounces) of fuel and changed the spacecraft's speed by 2.6 meters per second (about 5.8 mph).

"An almost six-miles-per-hour change may seem insignificant when we're closing in on the comet at 24,236 miles per hour [39,000 kilometers per hour]," said Tim Larson, Stardust-NExT project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "But we're still two weeks and 8.37 million miles [13.5 million kilometers] away from the comet. At that distance, our burn will move our location at time of closest approach to the comet by almost 1,900 miles [3,058 kilometers]. By observing the results of these planned maneuvers and making further rocket burns, that's how we get a spacecraft to be where we want it, when it's on the other side of the solar system."

NASA's plan for the Stardust-NExT mission is to fly the spacecraft to target a point in space about 200 kilometers (124 miles) from comet Tempel 1 at the time of its closest approach â€" about 8:56 p.m. PST on Feb. 14 (11:56 p.m. EST). This is a bonus mission for the comet chaser, which previously flew past comet Wild 2 and returned particles from its coma to Earth. During this bonus encounter, the spacecraft will take images of the comet's surface to observe what changes have occurred since a NASA spacecraft last visited. (NASA's Deep Impact executed an encounter with Tempel 1 in July 2005).

Along with the high-resolution images of the comet's surface, Stardust-NExT will also measure the composition, size distribution and flux of dust emitted into the coma, and provide important new information on how Jupiter-family comets evolve and how they formed 4.6 billion years ago. A Jupiter-family comet is a comet whose orbit has been modified by close passages to Jupiter. They have orbital periods less than 20 years.

Robert Pearlman

The Planetary Society contest

Are We There Yet?Measuring Stardust's Cosmic Journey

Stardust left Earth 12 years ago, carrying micro-etched names of more than a million people on a long journey through space. Since then Stardust has visited one comet, returned to fly past Earth, and is now on its way to a second comet.

How far do you think the journey has been for Stardust and the names chips?Enter your guess here; the ten closest guessers will win a cool Stardust T-shirt!

The ten entrants who guess closest to the actual distance that Stardust has traveled as of the moment of closest approach to Tempel 1 will receive a Stardust T-shirt and one year of membership in the Planetary Society.

Robert Pearlman

NASA Jet Propulsion Laboratory release

Stardust Celebrates Twelve Years With Rocket Burn

NASA's Stardust spacecraft marked its 12th anniversary in space on Monday, Feb. 7, with a rocket burn to further refine its path toward a Feb. 14 date with a comet.

The half-minute trajectory correction maneuver, which adjusts the spacecraft's flight path, began at about 1 p.m. PST (4 p.m. EST) on Monday, Feb. 7. The 30-second-long firing of the spacecraft's rockets consumed about 69 grams (2.4 ounces) of fuel and changed the spacecraft's speed by 0.56 meters per second (1.3 mph).

NASA's plan for the Stardust-NExT mission is to fly the spacecraft to a point in space about 200 kilometers (124 miles) from comet Tempel 1 at the time of its closest approach. During the encounter, the spacecraft will take images of the surface of comet Tempel 1 to observe what changes have occurred since a NASA spacecraft last visited. (NASA's Deep Impact flew by Tempel 1 in July 2005).

Along with the high-resolution images of the comet's surface, Stardust-NExT will also measure the composition, size distribution and flux of dust emitted into the coma, and provide important new information about how comets evolve.

Stardust was launched on Feb. 7, 1999. This current Stardust-NExT target is a bonus mission for the comet chaser, which flew past comet Wild 2 in 2004 and returned particles from its coma to Earth.

Robert Pearlman

NASA Stardust-NExT release

NASA Spacecraft Hours From Comet Encounter

As of today, Feb. 14, at 9:21 a.m. PST (12:21 p.m. EST), NASA's Stardust-NExT mission spacecraft is within a quarter-million miles (402,336 kilometers) of its quarry, comet Tempel 1, which it will fly by tonight. The spacecraft is cutting the distance with the comet at a rate of about 10.9 kilometers per second (6.77 miles per second or 24,000 mph).

Credit: NASA/JPL-Caltech/Cornell

Above:This composite image was taken by NASA's Stardust spacecraft 42 hours before its encounter with comet Tempel 1.

The flyby of Tempel 1 will give scientists an opportunity to look for changes on the comet's surface since it was visited by NASA's Deep Impact spacecraft in July 2005. Since then, Tempel 1 has completed one orbit of the sun, and scientists are looking forward to discovering any differences in the comet.

During the encounter phase, the spacecraft will carry out many important milestones in short order and automatically, as the spacecraft is too far away to receive timely updates from Earth. These milestones include turning the spacecraft to point its protective shields between it and the anticipated direction from which cometary particles would approach. Another milestone will occur at about four minutes to closest approach, when the spacecraft will begin science imaging of the comet's nucleus.

The nominal imaging sequence will run for about eight minutes. The spacecraft's onboard memory is limited to 72 high-resolution images, so the imaging will be most closely spaced around the time of closest approach for best-resolution coverage of Tempel 1's nucleus. At the time of closest encounter, the spacecraft is expected to be approximately 200 kilometers (124 miles) from the comet's nucleus.

The mission team expects to begin receiving images on the ground starting at around midnight PST (3 a.m. on Feb. 15 EST). Transmission of each image will take about 15 minutes. It will take about 10 hours to complete the transmission of all images and science data aboard the spacecraft.

Live coverage on NASA TV and via the Internet begins at 8:30 p.m. PST (11:30 p.m. EST) from mission control at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Coverage also will include segments from the Lockheed Martin Space System's mission support area in Denver. A post-flyby news conference is planned on Feb. 15 at 10 a.m. PST (1 p.m. EST).

The live coverage and news conference will also be carried on one of JPL's Ustream channels. During events, viewers can take part in a real-time chat and submit questions to the Stardust-NExT team.

During its 12 years in space, Stardust became the first spacecraft to collect samples of a comet (Wild 2 in 2004), which were delivered to Earth in 2006 for study. The Stardust-NExT mission is managed by JPL for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems in Denver built the spacecraft and manages day-to-day mission operations.

Robert Pearlman

NASA Stardust-NExT updates:

NASA's Stardust-NExT mission turned on its automatic navigation system in preparation to fly by comet Tempel 1 at about 10:40 p.m. CST.

As of about 10:41 p.m. CST, the spacecraft passed the point of closest approach with comet Tempel 1.

As of about midnight CST Feb. 15, Stardust turned to point its high-gain antenna at Earth and started downlinking data through that antenna.

It is expected to beam back the first images of Tempel 1 at around 2 a.m. CST, Feb. 15.

Robert Pearlman

NASA Jet Propulsion Laboratory release

NASA's Stardust Spacecraft Completes Comet Flyby

Mission controllers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., watched as data downlinked from the Stardust spacecraft indicated it completed its closest approach with comet Tempel 1. An hour after closest approach, the spacecraft turned to point its large, high-gain antenna at Earth. It is expected that images of the comet's nucleus collected during the flyby will be received on Earth starting at about midnight California time (3 a.m. EST on Tuesday, Feb. 15).

Preliminary data already transmitted from the spacecraft indicate the time of closest approach was about 8:39 p.m. PST (11:39 p.m. EST), at a distance of 181 kilometers (112 miles) from Tempel 1.

This is a bonus mission for the comet chaser, which previously flew past comet Wild 2 and returned samples from its coma to Earth. During this bonus encounter, the plan called for the spacecraft to take images of the comet's surface to observe what changes occurred since a NASA spacecraft last visited. (NASA's Deep Impact spacecraft executed an encounter with Tempel 1 in July 2005).

Stardust-NExT is a low-cost mission that will expand the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for NASA's Science Mission Directorate, Washington, D.C. Lockheed Martin Space Systems, Denver, built the spacecraft and manages day-to-day mission operations.

Robert Pearlman

Comet Hunter's First Images on the Ground

Mission controllers at NASA's Jet Propulsion Laboratory have begun receiving the first of 72 anticipated images of comet Tempel 1 taken by NASA's Stardust spacecraft.

Credit: NASA TV

Above:NASA's Stardust-NExT mission transmitted the first image it took during its approach to comet Tempel 1 at 8:35 p.m. PST on Feb. 14, 2011, from a distance of approximately 2,462 kilometers (1,530 miles).

The first six, most distant approach images are available on NASA's website. Additional images, including those from closest approach, are being downlinked in chronological order and will be available later in the day.

Mission managers had originally planned to receive the images taken during Stardust-NExT's closest approach first.

"We sent the commands that we had planned, anticipating the middle five images of the 72 image sequence would be played back," explained Chris Jones, JPL's associate director for flight projects and mission success. "What we got instead, we went to the top of the stack and the first picture that we received was the first image."

"It will take about six hours at the playback rate to get us to those five images," said Jones.

A news conference previously planned for 10 a.m. PST (1 p.m. EST) will be held later in the day, to allow scientists more time to analyze the data and images.

NASA's Stardust spacecraft returned new images of a comet showing a scar resulting from the 2005 Deep Impact mission. The images also showed the comet has a fragile and weak nucleus.

The spacecraft made its closest approach to comet Tempel 1 on Monday, Feb. 14, at 8:40 p.m. PST at a distance of approximately 111 miles. Stardust took 72 high-resolution images of the comet. It also accumulated 468 kilobytes of data about the dust in its coma, the cloud that is a comet's atmosphere. The craft is on its second mission of exploration called Stardust-NExT, having completed its prime mission collecting cometary particles and returning them to Earth in 2006.

The Stardust-NExT mission met its goals which included observing surface features that changed in areas previously seen during the 2005 Deep Impact mission; imaging new terrain; and viewing the crater generated when the 2005 mission propelled an impactor at the comet.

"This mission is 100 percent successful," said Joe Veverka, Stardust-NExT principal investigator of Cornell University, Ithaca, N.Y. "We saw a lot of new things that we didn't expect, and we'll be working hard to figure out what Tempel 1 is trying to tell us."

Several of the images provide tantalizing clues to the result of the Deep Impact mission's collision with Tempel 1.

Credit: NASA/JPL-Caltech/Cornell

"We see a crater with a small mound in the center, and it appears that some of the ejecta went up and came right back down," said Pete Schultz of Brown University, Providence, R.I. "This tells us this cometary nucleus is fragile and weak based on how subdued the crater is we see today."

Engineering telemetry downlinked after closest approach indicates the spacecraft flew through waves of disintegrating cometary particles including a dozen impacts that penetrated more than one layer of its protective shielding.

"The data indicate Stardust went through something similar to a B-17 bomber flying through flak in World War II," said Don Brownlee, Stardust-NExT co-investigator from the University of Washington in Seattle. "Instead of having a little stream of uniform particles coming out, they apparently came out in chunks and crumbled."

While the Valentine's Day night encounter of Tempel 1 is complete, the spacecraft will continue to look at its latest cometary obsession from afar.

"This spacecraft has logged over 3.5 billion miles since launch, and while its last close encounter is complete, its mission of discovery is not," said Tim Larson, Stardust-NExT project manager at JPL. "We'll continue imaging the comet as long as the science team can gain useful information, and then Stardust will get its well-deserved rest."

Robert Pearlman

NASA release

NASA's Venerable Comet Hunter Wraps up Mission

At 33 minutes after 4 p.m. PDT March 24, 2011, NASA's Stardust spacecraft finished its last transmission to Earth. The transmission came on the heels of the venerable spacecraft's final rocket burn, which was designed to provide insight into how much fuel remained aboard after its encounter with comet Tempel 1 in February.

"Stardust has been teaching us about our solar system since it was launched in 1999," said Stardust-NExT project manager Tim Larson from NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It makes sense that its very last moments would be providing us with data we can use to plan deep space mission operations in the future."

The burn to depletion maneuver was designed to fire Stardust's rockets until insufficient fuel remains to continue, all the while downlinking data on the burn to Earth some 312 million kilometers (194 million miles) away. Mission personnel will compare the amount of fuel consumed in the burn with the amount they anticipated would be burned based on their fuel consumption models.

Fuel consumption models are necessary because no one has invented a reliable fuel gauge for spacecraft when in the weightless environment of space flight. Until that day arrives, mission planners can approximate fuel usage by looking at the history of the vehicle's flight and how many times and for how long its rocket motors have fired.

Mission personnel watched the final data from the burn come down at JPL's Space Flight Operations Facility and at the Stardust-NExT mission support center at Lockheed Martin Space Systems in Denver.

"Stardust motors burned for 146 seconds," said Allan Cheuvront, Lockheed Martin Space Systems Company program manager for Stardust-NExT. "We'll crunch the numbers and see how close the reality matches up with our projections. That will be a great data set to have in our back pocket when we plan for future missions."

The Stardust team performed the final burn to depletion because NASA's most senior comet hunter is a spacecraft literally running on fumes. Launched on Feb. 7, 1999, Stardust had completed its prime mission back in January 2006. By that time, Stardust had already flown past an asteroid (Annefrank), flown halfway out to Jupiter to collect particle samples from the coma of a comet, Wild 2, and returned to fly by Earth to drop off a sample return capsule eagerly awaited by comet scientists. NASA then re-tasked the spacecraft to perform a bonus mission to fly past comet Tempel 1 to collect images and other scientific data. Stardust has traveled about 21 million kilometers (13 million miles) in its journey about the sun in the few weeks since the Valentine's day comet Tempel 1 flyby, making the grand total from launch to its final rocket burn about 5.69 billion kilometers (3.54 billion miles).

With all that mileage logged, the Stardust team knew the end was near. Now, with its fuel tank empty and its final messages transmitted, history's most traveled comet hunter will move from NASA's active mission roster to retired.

"This kind of feels like the end of one of those old Western movies where you watch the hero ride his horse towards the distant setting sun – and then the credits begin to roll," said Larson. "Only there's no setting sun in space."

Stardust-NExT was a low-cost mission to expand the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, managed the Stardust-NExT project for the NASA Science Mission Directorate, Washington, D.C., which was part of the Discovery Program managed by NASA's Marshall Space Flight Center in Huntsville, Ala. Joe Veverka of Cornell University, Ithaca, N.Y., was the mission's principal investigator. Lockheed Martin Space Systems, Denver, built the spacecraft and managed day-to-day mission operations.